Patent Application
20250154408
This application claims priority to and benefits of Korean Patent Application No. 10-2023-0155714 under 35 U.S.C. § 119, filed on Nov. 10, 2023, in the Korean Intellectual Property Office (KIPO), the entire contents of which are incorporated herein by reference.
Embodiments relate to quantum dots, methods of preparing quantum dots, and compositions and electronic devices including the quantum dots.
Quantum dots are nano crystals of a semiconductor material and are materials that exhibit a quantum confinement effect. When quantum dots receive light from an excitation source and reach an energy excited state, quantum dots emit energy according to the corresponding energy band gap. In this regard, even with a same material, the wavelength varies depending on particle size. Accordingly, by adjusting the size of the quantum dots, light in a desired wavelength range can be obtained and excellent color purity and high luminescence efficiency can be obtained. Therefore, quantum dots can be applied to various devices.
It is to be understood that this background of the technology section is, in part, intended to provide useful background for understanding the technology. However, this background of the technology section may also include ideas, concepts, or recognitions that were not part of what was known or appreciated by those skilled in the pertinent art prior to a corresponding effective filing date of the subject matter disclosed herein.
Embodiments include quantum dots with excellent chemical stability, photoluminescence properties, and dispersibility in hydrophilic solvents, a method of preparing the same, and a composition and an electronic device including the same.
Additional aspects will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the embodiments of the disclosure.
According to an embodiment, a quantum dot may include a nanoparticle and a heterofunctional ligand bound to the surface of the nanoparticle and represented by Formula 1:
M1(X1)(R1) [Formula 1]
In Formula 1,
According to an embodiment, M1 may be a cation of Zn, Cu, In, Ga, Cr, Mn, Fe, Co, Ni, Mg, Ca, Sc, Sn, Ti, V, Sr, Y, Zr, Nb, Mo, Cd, Ba, Au, Hg, Tl, or a combination thereof.
According to an embodiment, X1 may be Cl− or Br−.
According to an embodiment, R1 is a ligand represented by Formula 11:
*-L1-(R11)n1-T1 [Formula 11]
In Formula 11, L1 may be a linking group, R11 may be a hydrophilic unit, n1 may be an integer from 1 to 1,000, T1 may be a terminal group, and * may indicate a binding site to M1 in Formula 1.
According to an embodiment, in Formula 11, L1 may be a single bond, an ester group (—COO—), a carbonyl group (—CO—), an amide group (—C(═O)N—), an ether group (—O—), a sulfide group (—S—), a sulfoxide group (—SO—), a sulfonyl group (—SO2—), or a combination thereof.
According to an embodiment, in Formula 11, R11 may include at least one of a repeating unit represented by Formula 11-1 and a repeating unit represented by Formula 11-2:
In Formulae 11-1 and 11-2, R21 to R26 may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxy group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted C1-C60 heteroaryloxy group, a substituted or unsubstituted C1-C60 heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic heterocondensed polycyclic group.
According to an embodiment, in Formula 11, T1 may be hydrogen, deuterium, —OR31, —COOR31, —N(R31)(R32), —S(R31), or a C1-C20 alkyl group, and R31 and R32 may each independently be hydrogen, deuterium, or a C1-C20 alkyl group.
According to an embodiment, the heterofunctional ligand represented by Formula 1 is represented by Formula 21:
In Formula 21, T1 may be hydrogen, deuterium, —OR31, —COOR31, —N(R31)(R32), —S(R31), or a C1-C20 alkyl group, R31 and R32 may each independently be hydrogen, deuterium, or a C1-C20 alkyl group, and n1 may be an integer from 5 to 1,000.
According to an embodiment, the nanoparticle may include a core, and the core may include a Group I-III-VI compound.
According to an embodiment, the nanoparticle may further include a shell covering at least a portion of the core, and the shell may include a Group II-VI compound, a Group III-V compound, a Group III-VI compound, a Group I-III-VI compound, a Group II-IV-V compound, a Group II-V compound, a Group IV-V compound, or a combination thereof.
According to an embodiment, the core may include Cu, In, Ga, and Se, and the shell may include ZnS.
According to an embodiment, the nanoparticle has a diameter in a range of about 0.5 nm to about 7 nm.
According to an embodiment, a method of preparing quantum dots may include adding a heterofunctional ligand represented by Formula 1 to a solution including nanoparticles:
M1(X1)(R1) [Formula 1]
In Formula 1,
According to an embodiment, in the adding of the heterofunctional ligand to the solution, an organic ligand may be bonded to the nanoparticle, and the organic ligand and the heterofunctional ligand may undergo ligand exchange.
According to an embodiment, in the adding of the heterofunctional ligand to the solution, a content of the heterofunctional ligand may be in a range of about 10 parts by weight to about 30 parts by weight, based on 100 parts by weight of the nanoparticle.
According to an embodiment, the method may further include purifying and powdering the solution by adding an organic solvent to the solution.
According to an embodiment, a quantum dot composition may include the quantum dot.
According to an embodiment, the quantum dot composition may further include a crosslinkable monomer and an initiator.
According to an embodiment, an electronic device may include the quantum dot.
According to an embodiment, the electronic device may include an optoelectronic device including the quantum dot, and the optoelectronic device may be a photovoltaic device, a photodiode, a phototransistor, a photomultiplier, a photo resistor, a photo detector, a light sensitive detector, a solid-state triode, a battery electrode, a light-emitting device, a light-emitting diode, an organic light-emitting device, a quantum dot light-emitting diode, a transistor, a solar cell, a laser, or a diode injection laser.
The above and other aspects, features, and advantages of certain embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
The disclosure will now be described more fully hereinafter with reference to the accompanying drawings, in which embodiments are shown. This disclosure may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
In the drawings, the sizes, thicknesses, ratios, and dimensions of the elements may be exaggerated for ease of description and for clarity. Like numbers refer to like elements throughout.
In the description, it will be understood that when an element (or region, layer, part, etc.) is referred to as being “on”, “connected to”, or “coupled to” another element, it can be directly on, connected to, or coupled to the other element, or one or more intervening elements may be present therebetween. In a similar sense, when an element (or region, layer, part, etc.) is described as “covering” another element, it can directly cover the other element, or one or more intervening elements may be present therebetween.
In the description, when an element is “directly on,” “directly connected to,” or “directly coupled to” another element, there are no intervening elements present. For example, “directly on” may mean that two layers or two elements are disposed without an additional element such as an adhesion element therebetween.
As used herein, the expressions used in the singular such as “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. For example, “A and/or B” may be understood to mean “A, B, or A and B.” The terms “and” and “or” may be used in the conjunctive or disjunctive sense and may be understood to be equivalent to “and/or”.
In the specification and the claims, the term “at least one of” is intended to include the meaning of “at least one selected from the group of” for the purpose of its meaning and interpretation. For example, “at least one of A and B” may be understood to mean “A, B, or A and B.” When preceding a list of elements, the term, “at least one of,” modifies the entire list of elements and does not modify the individual elements of the list.
It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element.
Thus, a first element could be termed a second element without departing from the teachings of the disclosure. Similarly, a second element could be termed a first element, without departing from the scope of the disclosure.
The spatially relative terms “below”, “beneath”, “lower”, “above”, “upper”, or the like, may be used herein for ease of description to describe the relations between one element or component and another element or component as illustrated in the drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the drawings. For example, in the case where a device illustrated in the drawing is turned over, the device positioned “below” or “beneath” another device may be placed “above” another device. Accordingly, the illustrative term “below” may include both the lower and upper positions. The device may also be oriented in other directions and thus the spatially relative terms may be interpreted differently depending on the orientations.
The terms “about” or “approximately” as used herein is inclusive of the stated value and means within an acceptable range of deviation for the recited value as determined by one of ordinary skill in the art, considering the measurement in question and the error associated with measurement of the recited quantity (i.e., the limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within +20%, 10%, or ±5% of the stated value.
It should be understood that the terms “comprises,” “comprising,” “includes,” “including,” “have,” “having,” “contains,” “containing,” and the like are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof in the disclosure, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.
Unless otherwise defined or implied herein, all terms (including technical and scientific terms) used have the same meaning as commonly understood by those skilled in the art to which this disclosure pertains. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an ideal or excessively formal sense unless clearly defined in the specification.
The term “Group II” used herein may include a Group IIA element and a Group IIB element on the IUPAC periodic table, and examples of the Group II element may include Zn, Cd, Hg, and Cn, but the disclosure is not limited thereto.
The term “Group III” as used herein may include a Group IIIA element and a Group IIIB element on the IUPAC periodic table, and examples of the Group III element may include Al, In, Ga, Tl, and Nh, but the disclosure is not limited thereto.
The term “Group V” used herein may include a Group VA element and a Group VB element on the IUPAC periodic table, and examples of the Group V element may include N, P, and As, but the disclosure is not limited thereto.
The term “Group VI” used herein may include a Group VIA element and a Group VIB element on the IUPAC periodic table, and examples of the Group VI element may include O, S, Se, and Te, but the disclosure is not limited thereto.
M1(X1)(R1) [Formula 1]
In Formula 1,
A quantum dot according to an embodiment may include a heterofunctional ligand 20 bonded to the surface of a nanoparticle 10, and accordingly, surface defects due to substitution of ligands may be reduced.
Typically, in the synthesis step of quantum dots, a non-coordinate solvent having a high boiling point and a hydrophobic ligand may be used. For the subsequent process, quantum dots may need to be used in the form of an ink composition. To the end, ligand exchange may be needed to replace the hydrophobic ligand with a hydrophilic ligand. Conventionally, during this process, part of the surface of the nanoparticle may be torn off together with the hydrophobic ligand, creating permanent defects on the surface of the quantum dot, resulting in a loss of quantum yield of the quantum dot, and a charge may be generated on the surface defect and thus quantum dots may aggregate and dispersibility may be reduced. In the case of quantum dots having relatively small average sizes, for example, CIGS (Cu—In—Ga—S) quantum dots, quantum yield loss and dispersibility deterioration may occur significantly.
Quantum dots according to embodiments may have a structure in which a heterofunctional ligand is bonded to the surface of a nanoparticle and thus, steric hindrance during the ligand exchange process may be reduced so that the surface of the quantum dot may be effectively modified without surface defects. As the heterofunctional ligand includes R1, which is a hydrophilic group having 11 or more carbon atoms, dispersibility of quantum dots in hydrophilic solvents may be improved.
Therefore, quantum dots according to embodiments may have excellent chemical stability and photoluminescence properties, and have excellent dispersibility in solvents. Accordingly, such quantum dots may be suitable for application to ink compositions. By using such quantum dots and/or methods of preparing the quantum dots, high-quality electronic devices may be provided.
According to an embodiment, M1 may be a cation of Zn, Cu, In, Ga, Cr, Mn, Fe, Co, Ni, Mg, Ca, Sc, Sn, Ti, V, Sr, Y, Zr, Nb, Mo, Cd, Ba, Au, Hg, Tl, or a combination thereof.
According to an embodiment, M1 may be a cation of a Group II element.
According to an embodiment, M1 may be Zn2+.
According to an embodiment, X1 may be F−, Cl−, Br− or I−.
According to an embodiment, X1 may be Cl− or Br−.
According to an embodiment, R1 may be a hydrophilic group having 11 to 50 carbon atoms. For example, R1 may be a hydrophilic group having 11 to 30 carbon atoms. For example, R1 may be a hydrophilic group having 11 to 20 carbon atoms.
According to an embodiment, R1 may be a ligand represented by Formula 11 below:
*-L1-(R11)n1-T1 [Formula 11]
In Formula 11,
According to an embodiment, L1 may be a single bond, an ester group (—COO—), a carbonyl group (—CO—), an amide group (—C(═O)N—), an ether group (—O—), a sulfide group (—S—), a sulfoxide group (—SO—), a sulfonyl group (—SO2−), or a combination thereof.
According to an embodiment, R11 may include at least one of a repeating unit represented by Formula 11-1 and a repeating unit represented by Formula 11-2.
In Formulae 11-1 and 11-2,
R21 to R26 may each independently be hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxy group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted C1-C60 heteroaryloxy group, a substituted or unsubstituted C1-C60 heteroarylthio group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, or a substituted or unsubstituted monovalent non-aromatic heterocondensed polycyclic group.
According to an embodiment, R21 to R26 may each independently be:
According to an embodiment, T1 may be hydrogen, deuterium, —OR31, —COOR31, —N(R31)(R32), —S(R31), or a C1-C20 alkyl group, and
According to an embodiment, the heterofunctional ligand represented by Formula 1 may be represented by Formula 21:
In Formula 21,
T1 may be hydrogen, deuterium, —OR31, —COOR31, —N(R31)(R32), —S(R31), or a C1-C20 alkyl group,
According to an embodiment, the heterofunctional ligand represented by Formula 1 may be electrically neutral.
According to an embodiment, the nanoparticle 10 may include a core.
According to an embodiment, the core may include a Group II-VI compound, a Group III-VI compound, a Group III-V compound, a Group IV-VI compound, a Group IV element or compound, a Group I-III-VI compound, or a combination thereof.
The Group II-VI compound may include: a binary compound such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, MgS, and a combination thereof; a ternary compound such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS, a combination thereof; and a quaternary compound such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, HgZnSTe, and a combination thereof.
The Group III-VI compounds may include: a binary compound, such as In2S3 or In2Se; a ternary compound, such as InGaS3 or InGaSes; or a combination thereof.
For example, the Group III-V compound may include: a binary compound such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, InSb, and a combination thereof; a ternary compound such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InAlP, InNP, InNAs, InNSb, InPAs, InPSb, GaAlNP, and a combination thereof; and a quaternary compound such as GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, InAlPSb, and a combination thereof. The Group III-V semiconductor compound may further include Group II metal (for example, InZnP, etc.).
The Group IV-VI compound may include: a binary compound such as SnS, SnSe, SnTe, PbS, PbSe, PbTe, and a combination thereof; a ternary compound such as SnSeS, SnSeTe, SnSTe, PbSeS, PbSeTe, PbSTe, SnPbS, SnPbSe, SnPbTe, and a combination thereof; and a quaternary compound such as SnPbSSe, SnPbSeTe, SnPbSTe, and a combination thereof.
The Group IV element may include Si, Ge, and a combination thereof. The Group IV compound may be a binary compound such as SiC, SiGe, and a combination thereof.
The Group I-III-VI compound may be a ternary compound, such as AgInS, AgInS2, CuInS, CuInS2, CuGaO2, AgGaO2, AgAlO2, etc., or a combination thereof.
The binary compound, the ternary compound, or the quaternary compound may exist in particles at uniform concentration, or may exist in a particle while the binary compound, the ternary compound, and the quaternary compound have different concentration distributions.
According to an embodiment, the core may include a Group I-III-VI compound.
According to an embodiment, Group I-III-VI compound may be represented by Formula 101:
(M11)a11(M12)a12(M13)a13(M14)2 [Formula 101]
In Formula 101,
According to an embodiment, M11 may be Cu, M12 may be In, M13 may be Ga, and M14 may be 0, S, or Se.
According to an embodiment, the nanoparticle 10 may further include a shell which covers at least a portion of the core. In an embodiment, the nanoparticle may have a core/shell structure. Hereinafter, the shell will be referred to as a first shell. An interface between the core and the shell may have a concentration gradient in which the concentration of an element present in the shell decreases toward the core.
According to an embodiment, the first shell may include a Group II-VI compound, a Group III-VI compound, a Group III-VI compound, a Group II-III-VI compound, or a combination thereof.
Examples of the Group III-VI compound may include a binary compound such as InS, InS2, GaO2, GaS2, or AlO2; or a combination thereof.
Examples of the Group II-III-VI compound may include: a ternary compound, such as CdGaS, CdGaSe, CdGa2Se3, CdGaTe, CdInS, CdInSe, CdIn2S3, CdIn2Se3, CdInTe, ZnGaS, ZnGaSe, ZnGa2Se3, ZnGaTe, ZnInS, ZnInSe, ZnIn2S3, ZnIn2Se3, ZnInTe, HgGaS, HgGaSe, HgGa2Se3, HgGaTe, HgInS, HgInSe, HgIn2S3, HgIn2Se3, or HgInTe; a quaternary compound, such as CdInGaS3, CdInGaSe3, ZnInGaS3, ZnInGaSe3, HgInGaS3, or HgInGaSe3; or a combination thereof.
According to an embodiment, the first shell may include a compound represented by Formula 201:
(M21)a21(M22)a22(M23)a23 [Formula 201]
In Formula 201,
According to an embodiment, M1 included in the heterofunctional ligand and M21 included in the first shell may be the same element.
According to an embodiment, the first shell may include CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, or a combination thereof.
According to an embodiment, the core may include Cu, In, Ga, and Se, and the first shell may include ZnS.
According to an embodiment, a thickness of the first shell may be in a range of about 0.1 nm to about 5 nm. For example, a thickness of the first shell may be in a range of about 0.2 nm to about 4 nm. For example, a thickness of the first shell may be in a range of about 0.2 nm to about 3 nm. For example, a thickness of the first shell may be in a range of about 0.4 nm to about 2 nm. For example, a thickness of the first shell may be in a range of about 0.5 nm to about 1 nm.
The emission wavelength of the quantum dot may be adjusted by ensuring that the thickness of the first shell satisfies these ranges. For example, the quantum dot may not emit light having a long wavelength by ensuring that the thickness of the first shell satisfies these ranges.
According to an embodiment, the quantum dot may further include a second shell covering at least a portion of the first shell.
According to an embodiment, the second shell may include a Group II-VI compound, a Group III-V compound, a Group III-VI compound, a Group I-III-VI compound, a Group II-III-VI compound, a Group II-IV-V compound, a Group II-V compound, a Group IV-V compound, or a combination thereof.
Examples of the Group II-VI compound may include: a binary compound such as CdS, CdSe, CdTe, ZnS, ZnSe, ZnTe, ZnO, HgS, HgSe, HgTe, MgSe, or MgS; a ternary compound such as CdSeS, CdSeTe, CdSTe, ZnSeS, ZnSeTe, ZnSTe, HgSeS, HgSeTe, HgSTe, CdZnS, CdZnSe, CdZnTe, CdHgS, CdHgSe, CdHgTe, HgZnS, HgZnSe, HgZnTe, MgZnSe, MgZnS; a quaternary compound such as CdZnSeS, CdZnSeTe, CdZnSTe, CdHgSeS, CdHgSeTe, CdHgSTe, HgZnSeS, HgZnSeTe, or HgZnSTe; or a combination thereof.
Examples of the Group III-V compound may include: a binary compound such as GaN, GaP, GaAs, GaSb, AlN, AlP, AlAs, AlSb, InN, InP, InAs, or InSb; a ternary compound such as GaNP, GaNAs, GaNSb, GaPAs, GaPSb, AlNP, AlNAs, AlNSb, AlPAs, AlPSb, InGaP, InNP, InAlP, InNAs, InNSb, InPAs, or InPSb; a quaternary compound such as GaAlNP, GaAlNAs, GaAlNSb, GaAlPAs, GaAlPSb, GaInNP, GaInNAs, GaInNSb, GaInPAs, GaInPSb, InAlNP, InAlNAs, InAlNSb, InAlPAs, or InAlPSb; or a combination thereof. The Group III-V compound may further include a Group II element. Examples of Group II-III-V compound further including a Group II element may include InZnP, InGaZnP, and InAlZnP.
Examples of the Group III-VI compounds may refer to those described herein.
Examples of the Group I-III-VI compounds may include a ternary compound such as AgInS, AgInS2, CuInS, CuInS2, CuGaO2, AgGaO2, or AgAlO2; or a combination thereof.
Examples of the Group II-III-VI compound may refer to those described herein.
Examples of the Group II-IV-V compound may include ZnSnP2, ZnSnAs2, and ZnSnSb2.
Examples of the Group II-V compound may include ZnP, ZnAs, and ZnSb.
Examples of the Group IV-VI compound may include: a binary compound such as SnS, SnSe, SnTe, PbSe, PbS, or PbTe; a ternary compound such as SnSeS, SnSeTe, SnSTe, SnPbS, SnPbSe, SnPbTe, PbSTe, PbSeS, or PbSeTe; a quaternary compound such as SnPbSSe, SnPbSeTe, or SnPbSTe; or a combination thereof.
According to an embodiment, the second shell may include ZnS, ZnSe, ZnTe, ZnO, ZnSeS, ZnSeTe, ZnSTe, or a combination thereof.
According to an embodiment, a thickness of the second shell may be in a range of about 0.1 nm to about 5 nm. For example, a thickness of the second shell may be in a range of about 0.2 nm to about 4 nm. For example, a thickness of the second shell may be in a range of about 0.2 nm to about 3 nm. For example, a thickness of the second shell may be in a range of about 0.4 nm to about 2 nm. For example, a thickness of the second shell may be in a range of about 0.5 nm to about 1 nm.
According to an embodiment, a diameter of the nanoparticle may be in a range of about 0.5 nm to about 8 nm. For example, a diameter of the nanoparticle may be in a range of about 1 nm to about 7.5 nm. For example, a diameter of the nanoparticle may be in a range of about 2 nm to about 7 nm.
According to an embodiment, a diameter of the quantum dot may be in a range of about 1 nm to about 15 nm. For example, a diameter of the quantum dot may be in a range of about 1 nm to about 12 nm. For example, a diameter of the quantum dot may be in a range of about 1 nm to about 10 nm.
According to an embodiment, the quantum dot may not include cadmium.
Accordingly, the quantum dot may not have issues due to the high toxicity of cadmium.
According to an embodiment, the quantum dot may have a maximum emission wavelength in a range of about 200 nm to about 800 nm.
According to an embodiment, the quantum dot may emit red light with a maximum emission wavelength in a range of about 590 nm to about 750 nm.
According to an embodiment, the quantum dot may emit green light with a maximum emission wavelength in a range of about 490 nm to about 590 nm.
According to an embodiment, the quantum dot may emit blue light with a maximum emission wavelength in a range of about 410 nm to about 490 nm.
According to an embodiment, the quantum dots may emit deep blue light with a maximum emission wavelength in a range of about 410 nm to about 465 nm.
According to an embodiment, the quantum dot may have a roundness in a range of about 0.7 to about 0.9.
The shape of the quantum dot is not specifically limited, and may be one commonly used in the art. For example, the quantum dot may have a form of spherical, pyramidal, multi-arm, or cubic nanoparticles, nanotubes, nanowires, nanofibers, nanoplate-shaped particles, etc.
According to an embodiment, the quantum dot may have a full width of half maximum (FWHM) of the photoluminescence (PL) spectrum of less than or equal to about 60 nm. For example, the quantum dot may have a full width of half maximum (FWHM) of the photoluminescence (PL) spectrum of less than or equal to about 55 nm. For example, the quantum dot may have a full width of half maximum (FWHM) of the photoluminescence (PL) spectrum of less than or equal to about 50 nm. For example, the quantum dot may have a full width of half maximum (FWHM) of the photoluminescence (PL) spectrum of less than or equal to about 40 nm. In case that the FWHM of the quantum dot satisfies these values, color purity and color reproducibility may be excellent, and the wide viewing angle may be improved.
According to an embodiment, the quantum dot may have a quantum yield of greater than or equal to about 70%. For example, the quantum dot may have a quantum yield of greater than or equal to about 80%. For example, the quantum dot may have a quantum yield of greater than or equal to about 90%.
According to an embodiment, the quantum dot may have, after purification with ethanol, a quantum yield of greater than or equal to about 70%. For example, the quantum dot may have, after purification with ethanol, a quantum yield of greater than or equal to about 80%. For example, the quantum dot may have, after purification with ethanol, a quantum yield of greater than or equal to about 90%.
A method of preparing quantum dots according to an embodiment may include adding a heterofunctional ligand represented by Formula 1 to a solution containing nanoparticles.
M1(X1)(R1) [Formula 1]
In Formula 1,
According to an embodiment, in the adding of the heterofunctional ligand to the solution, the content of the heterofunctional ligand may be, based on 100 parts by weight of the nanoparticle, in a range of about 5 parts by weight to about 50 parts by weight. For example, the content of the heterofunctional ligand may be, based on 100 parts by weight of the nanoparticle, in a range of about 10 parts by weight to about 30 parts by weight.
According to an embodiment, the method of preparing the quantum dot may further include heating the solution at a temperature in a range of about 50° C. to about 90° C. For example, the solution may be heated at a temperature in a range of about 60° C. to about 80° C.
According to an embodiment, the heating may be performed for about 30 minutes to about 3 hours. For example, the heating may be performed for about 1 hour to about 2 hours.
According to an embodiment, the method of preparing the quantum dot may further include purifying and powdering by adding an organic solvent to the solution.
According to an embodiment, the surface of the nanoparticle may be treated with an organic ligand or a metal halide.
According to an embodiment, an organic ligand may be bonded to the nanoparticle, and due to the addition of the heterofunctional ligand to the solution, the organic ligand and the heterofunctional ligand may undergo ligand exchange.
According to an embodiment, the organic ligand may include a C4-C30 fatty acid.
For example, the organic ligand may include palmitic acid, palmitoleic acid, stearic acid, oleic acid, trioctylphosphine, trioctylphosphine oxide, oleylamine, octylamine, trioctyl amine, hexadecylamine, octanethiol, dodecanethiol, hexylphosphonic acid, tetradecylphosphonic acid, or octylphosphonic acid.
According to an embodiment, the metal halide may be a metal halide represented by Formula 10:
Am+(X−)m [Formula 10]
In Formula 10,
According to an embodiment, the metal halide may be zinc halide, indium halide, aluminum halide, gallium halide, or a combination thereof.
According to an embodiment, the metal halide may be ZnCl2, InCl3, AlCl3, GaCl3, NaCl, ZnI2, AlI3, GaI3, or a combination thereof.
According to an embodiment, the solution may include a solvent.
According to an embodiment, the solvent may include cyclohexyl acetate, 1-octadecene (ODE), trioctylamine (TOA), trioctylphosphine (TOP), or a combination thereof.
According to an embodiment, a quantum dot composition including the quantum dot may be provided.
According to an embodiment, the quantum dot composition may further include a crosslinkable monomer.
For example, the crosslinkable monomer may be 1,6-hexanediol diacrylate (HDDA), 2-ethylhexyl(meth)acrylate, ethyl(meth)acrylate, methyl(meth)acrylate, n-propyl(meth)acrylate, isopropyl(meth)acrylate, pentyl(meth)acrylate, n-octyl(meth)acrylate, isooctyl(meth)acrylate, isononyl(meth)acrylate, n-butyl(meth)acrylate, isobutyl(meth)acrylate, n-hexyl(meth)acrylate, n-nonyl(meth)acrylate, isoamyl(meth)acrylate, n-decyl(meth)acrylate, isodecyl(meth)acrylate, dodecyl(meth)acrylate, isobornyl(meth)acrylate, cyclohexyl(meth)acrylate, phenyl(meth)acrylate, benzyl(meth)acrylate, isostearyl(meth)acrylate, 2-methylbutyl(meth)acrylate, or a combination thereof.
According to an embodiment, the crosslinkable monomer may be hydrophilic.
According to an embodiment, a weight ratio of the quantum dot to the crosslinkable monomer in the quantum dot composition may be in a range of about 1:0.1 to about 1:10. For example, a weight ratio of the quantum dot to the crosslinkable monomer in the quantum dot composition may be in a range of about 1:0.2 to about 1:5. For example, a weight ratio of the quantum dot to the crosslinkable monomer in the quantum dot composition may be in a range of about 1:0.5 to about 1:2.
According to an embodiment, the quantum dot composition may further include an initiator.
For example, the initiator may include diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 4-acryloxybenzophenone, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenyl-1-propan-1-one, ethyl(2,4,6-trimethylbenzoyl)phenyl phosphinate, bisacylphosphine oxide, or a combination thereof.
According to an embodiment, a viscosity (@25° C.) of the quantum dot composition may be in a range of about 2 cP to about 30 cP.
In case that the viscosity of the quantum dot composition satisfies this range, the quantum dot composition may be suitable for forming a layer using a solution process, for example, spin coating or inkjet.
According to an embodiment, the quantum dot composition may further include a solvent.
According to an embodiment, the solvent may be a hydrophilic solvent. For example, the solvent may be 1,6-hexanediol diacrylate (HDDA).
According to an embodiment, an electronic device including the quantum dot may be provided.
The quantum dot may be included in various electronic devices. For example, an electronic device including the quantum dot may be a light-emitting device, an authentication device, etc.
The electronic device (for example, a light-emitting device or a display device) may further include a light-emitting device and a color filter, a color conversion layer, or a color filter and a color conversion layer. The color filter and/or the color conversion layer may be disposed in at least one of directions in which light emitted from a light-emitting device travels. For example, light emitted from the light-emitting device may be blue light or white light. According to an embodiment, the light-emitting device may include a quantum dot. According to an embodiment, the color conversion layer may include a quantum dot. The quantum dot may be, for example, the quantum dot as described herein.
The electronic device may be applied to various displays, a light source, an illuminator, a personal computer (for example, a mobile personal computer), a mobile phone, a digital camera, an electronic notebook, an electronic dictionary, an electronic game machine, a medical apparatus (for example, an electronic thermometer, a blood pressure monitor, a blood glucose meter, a pulse measuring device, a pulse wave measuring device, an electrocardiogram display device, an ultrasonic diagnostic device, or an endoscope display device), a fish detector, various measuring devices, instruments (for example, instruments for vehicles, aircrafts, or ships), a projector, or the like.
According to an embodiment, the electronic device may include an optoelectronic device including the quantum dot, and
the optoelectronic device may be a photovoltaic device, a photodiode, a phototransistor, a photomultiplier, a photo resistor, a photo detector, a light sensitive detector, a solid-state triode, a battery electrode, a light-emitting device, a light-emitting diode, an organic light-emitting device, a quantum dot light-emitting diode, a transistor, a solar cell, a laser, or a diode injection laser.
According to an embodiment, an electronic device 200 may include a light source 220 and a color conversion member 230 disposed in a path of light emitted from the light source 220, and the quantum dot may be included in the color conversion member 230.
For example, the light source 220 may be a back light unit (BLU) used in a liquid crystal display (LCD), a fluorescent lamp, a light-emitting device, an organic light-emitting device, a quantum dot light-emitting device (QLED), or a combination thereof. The color conversion member 230 may be arranged in at least one of directions in which light emitted from the light source 220 travels.
At least one region of the color conversion member 230 of the electronic device 200 may include the quantum dot, and the region may absorb light emitted from the light source and emit blue light with a maximum emission wavelength in a range of about 410 nm to about 490 nm.
That the color conversion member 230 is arranged in at least one of directions in which the light emitted from the light source 220 travels, may not exclude other elements from being further included between the color conversion member 230 and the light source 220.
For example, a polarizer, a liquid crystal layer, a light guide plate, a diffusion plate, a prism sheet, a microlens sheet, a brightness enhancement sheet, a reflective film, a color filter, or a combination thereof may be disposed between the light source 220 and the color conversion member 230.
In another embodiment, a polarizer, a liquid crystal layer, a light guide plate, a diffusion plate, a prism sheet, a microlens sheet, a brightness enhancement sheet, a reflective film, a color filter, or a combination thereof may be disposed on the color conversion member 230.
The light source 220 may be a backlight unit (BLU) or a light emitting device for use in liquid crystal displays (LCD), a fluorescent lamp, a light-emitting diode (LED), an organic light-emitting device (OLED), or a quantum-dot light-emitting device (QLED), but the disclosure is not limited thereto.
The light emitted from the light source as described above may be light-converted while passing through the quantum dot. For example, the quantum dot may absorb the first light emitted from the light source and emit a visible light different from the first light. For example, the quantum dot may absorb ultraviolet (UV) light emitted from the light source and emit visible light having a maximum emission wavelength in a range of about 410 nm to about 750 nm. In an embodiment, the quantum dot may absorb blue light emitted from the light source and emit visible light having a maximum emission wavelength in a range of about 495 nm to about 750 nm. Accordingly, the quantum dot or a color conversion member including the quantum dot may be designed to absorb UV light or blue light emitted from a light source and emit wavelengths of various color ranges.
In an embodiment, the quantum dot may absorb blue light emitted from the light source and emit green light having a maximum emission wavelength in a range of about 495 nm to about 570 nm. For example, the quantum dot may absorb blue light emitted from the light source and emit a red light having a maximum emission wavelength in a range of about 630 nm to about 750 nm.
Accordingly, the quantum dot or a color conversion member including the quantum dot may absorb light emitted from a light source and produce blue, green, or red colors with high brightness and high color purity.
The electronic device 200 shown in
In another embodiment, the electronic device may include a structure including a light source, a light guide plate, a color conversion member, a first polarizing plate, a liquid crystal layer, a color filter, and a second polarizing plate that are sequentially arranged.
In another embodiment, the electronic device may include a structure including a light source, a light guide plate, a first polarizing plate, a liquid crystal layer, a second polarizing plate, and a color conversion member that are sequentially arranged.
In the embodiments described above, the color filter may include a pigment or a dye. In the embodiments described above, one of the first polarizing plate and the second polarizing plate may be a vertical polarizing plate, and another one of the first polarizing plate and the second polarizing plate may be a horizontal polarizing plate.
In another embodiment, the quantum dot as described in the specification may be used as an emitter. According to another embodiment, an electronic device may include a light-emitting device that includes a first electrode, a second electrode facing the first electrode, and an emission layer arranged between the first electrode and the second electrode, and the light-emitting device (for example, the emission layer of the light-emitting device) may include the quantum dot. The light-emitting device may further include a hole transport region between the first electrode and the emission layer, an electron transport region between the emission layer and the second electrode, or a combination thereof.
The interlayer 330 may be disposed on the first electrode 310. The interlayer 330 may include an emission layer.
The interlayer 330 may further include a hole transport region disposed between the first electrode 310 and the emission layer and an electron transport region disposed between the emission layer and the second electrode 350.
In addition to the quantum dot, the interlayer 330 may further include metal-containing compounds such as an organometallic compound, an organic material, etc.
The hole transport region and the electron transport region may respectively include hole transporting materials and/or electron transporting materials commonly used in organic light-emitting devices.
The interlayer 330 may include two or more emitting units sequentially stacked between the first electrode 310 and the second electrode 350, and a charge generation layer disposed between two adjacent emitting units. In case that the interlayer 330 includes the emitting unit and the charge generation layer as described above, the light-emitting device 300 may be a tandem light-emitting device.
The emission layer may be a quantum dot single layer or a structure in which two or more quantum dot layers are stacked each other. For example, the emission layer may be a quantum-dot single layer or a multilayer structure in which 2 to 100 quantum dot layers are stacked each other.
The emission layer may include the quantum dot as described herein.
The emission layer may further include a different quantum dot in addition to the quantum dot as described herein.
The emission layer may further include, in addition to the quantum dot as described herein, a dispersion medium in which the quantum dots are dispersed in a naturally coordinated form. The dispersion medium may include an organic solvent, a polymer resin, or a combination thereof. The dispersion medium may be a transparent medium that does not affect the optical performance of the quantum dot, is not deteriorated by light, does not reflect light, or does not absorb light. For example, the organic solvent may include toluene, chloroform, ethanol, octane, or a combination thereof, and the polymer resin may include an epoxy resin, a silicone resin, a polystyrene resin, an acrylate resin, or a combination thereof.
The emission layer may be formed by coating, on the hole transport region, a quantum dot-containing composition for forming the emission layer, and volatilizing a portion or more of the solvent from the composition for forming the emission layer.
For example, water, hexane, chloroform, toluene, octane, etc. may be used as a solvent included in the composition for forming the emission layer.
The coating of the composition for forming the emission layer may be performed using a spin coat method, a casting method, a micro gravure coating method, a gravure coating method, a bar coating method, a roll coating method, a wire bar coating method, a dip coating method, a spray coating method, a screen printing method, a flexographic method, an offset printing method, an ink jet printing method, or the like.
In case that the light-emitting device 300 is a full-color light-emitting device, the emission layer may include an emission layer that emits light of different colors for each subpixel.
In an embodiment, the emission layer may be patterned, for each subpixel, as a first color emission layer, a second color emission layer, and a third color emission layer. At least one emission layer of the emission layers described above may essentially include the quantum dot. For example, the first-color emission layer may be a quantum-dot emission layer including the quantum dot, and the second-color emission layer and the third-color emission layer may be organic emission layers including organic compounds. In this regard, the first color through the third color may be different colors, and for example, the first color through the third color may have different maximum emission wavelengths. The first color through the third color may be white when combined with each other.
In an embodiment, the emission layer may further include a fourth color emission layer, and at least one emission layer of the first color to fourth color emission layers may be a quantum dot emission layer including the quantum dot, and the remaining emission layers may be organic emission layers including organic compounds. Other various modifications may be possible. In this regard, the first color through the fourth color may be different colors, and for example, the first color through the fourth color may have different maximum emission wavelengths. The first color through the fourth color may be white when combined with each other.
In another embodiment, the light-emitting device 300 may have a structure in which two or more emission layers emitting light of the same or different colors are stacked in contact with or spaced apart from each other. At least one of the two or more emission layers may be a quantum dot emission layer including the quantum dots, and another emission layer may be an organic emission layer including organic compounds. Such a variation may be made. In some embodiments, the light-emitting device 300 may include a first color emission layer and a second color emission layer, and the first color and the second color may be a same color or different colors. For example, the first color and the second color may be both blue.
In addition to quantum dots, the emission layer may further include one or more types of organic compounds of compounds.
For example, the organic compound may include a host and a dopant. The host and the dopant may include a host and a dopant that are commonly used in organic light-emitting devices, respectively.
For example, the semiconductor compound may be an organic and/or inorganic perovskite.
The electronic device (for example, the light-emitting device) may further include a color filter, a color conversion layer, or a color filter and a color conversion layer in addition to the light-emitting device. The color filter and/or the color conversion layer may be disposed in at least one traveling direction of light emitted from the light-emitting device. For example, light emitted from the light-emitting device may be blue light or white light. For a description of the light-emitting device, reference may be made to those described above. According to an embodiment, the color conversion layer may include a quantum dot. The quantum dot may be, for example, the quantum dot as described herein.
The electronic device may include a first substrate. The first substrate may include multiple subpixel regions, the color filter may include multiple color filter regions corresponding to the subpixel regions, respectively, and the color conversion layer may include multiple color conversion regions corresponding to the subpixel regions, respectively.
A pixel defining layer may be disposed between the subpixel regions to define each subpixel region.
The color filter may further include multiple color filter regions and light blocking patterns disposed between the color filter regions, and the color conversion layer may further include multiple color conversion regions and light blocking patterns disposed between the color conversion regions.
The color filter regions (or the color conversion regions) may include a first region configured to emit first color light, a second region configured to emit second color light, and/or a third region configured to emit third color light, and the first color light, the second color light, and/or the third color light may have different maximum emission wavelengths. For example, the first color light may be red light, the second color light may be green light, and the third color light may be blue light. For example, the color filter regions (or the color conversion regions) may include quantum dots. For example, the first region may include a red quantum dot, the second region may include a green quantum dot, and the third region may not include a quantum dot. For a description of the quantum dot, reference may be made to those described herein. Each of the first region, the second region, and/or the third region may further include a scatterer.
For example, the light-emitting device may be configured to emit first light, the first region may be configured to absorb the first light to emit first-1 color light, the second region may be configured to absorb the first light to emit second-1 color light, and the third region may be configured to absorb the first light to emit third-1 color light. The first-1 color light, the second-1 color light, and the third-1 color light may have different maximum emission wavelengths. In some embodiments, the first light may be blue light, the first-1 color light may be red light, the second-1 color light may be green light, and the third-1 color light may be blue light.
The electronic device may further include a thin film transistor in addition to the light-emitting device described above. The thin-film transistor may include a source electrode, a drain electrode, and an active layer, and one of the source electrode and the drain electrode may be electrically connected to one of the first electrode and the second electrode of the light-emitting device.
The thin-film transistor may further include a gate electrode, a gate insulating film, and the like.
The active layer may include crystalline silicon, amorphous silicon, an organic semiconductor, an oxide semiconductor, or the like.
The electronic device may further include an encapsulation unit configured to seal the light-emitting device. The encapsulation unit may be disposed between the color filter and/or color conversion layer and the light-emitting device. The encapsulation unit may allow light from the light-emitting device to be emitted to the outside and concurrently may block external air and moisture from permeating into the light-emitting device. The encapsulation unit may be an encapsulation substrate including a transparent glass substrate or a plastic substrate. The encapsulation unit may be a thin film encapsulation layer including at least one of an organic layer and an inorganic layer. In case that the encapsulation unit is a thin film encapsulation layer, the electronic device may be flexible.
In addition to the color filter and/or the color conversion layer, various functional layers may be additionally disposed on the encapsulation unit according to the use of the electronic device. Examples of the functional layer may include a touch screen layer, a polarization layer, and the like. The touch screen layer may be a resistive touch screen layer, a capacitive touch screen layer, or an infrared touch screen layer. The authentication device may be, for example, a biometric authentication device that identifies an individual by using biometric information of a living body (e.g., a fingertip, a pupil, or the like).
The authentication device may further include a biometric information collecting unit in addition to the light-emitting device described above.
The electronic device may be applied to various display devices, a light source, an illuminator, a personal computer (for example, a mobile personal computer), a mobile phone, a digital camera, an electronic notebook, an electronic dictionary, an electronic game machine, a medical device (for example, an electronic thermometer, a blood pressure monitor, a blood glucose meter, a pulse measuring device, a pulse wave measuring device, an electrocardiogram display device, an ultrasonic diagnostic device, or an endoscope display device), a fish detector, various measuring devices, instruments (for example, instruments for vehicles, aircrafts, or ships), a projector, or the like.
Hereinafter, quantum dots and methods of preparing of quantum dots according to embodiments will be described in more detail through Examples.
Deionized water (DI) containing 5 wt % of NaOH was added to a 15 v/v % mPEG5-COOH (in ethanol) solution and stirred at 25° C. until the pH reached 7 to obtain Na(COO-PEG5m)2.
The compound [Na(COO-PEG5m)2] obtained above was purified and mixed with zinc chloride at a molar ratio of 1:1 in a mixed solution including 80 ml of ethanol, 60 ml of DI water, and 140 ml of hexane. The resultant solution was stirred at a temperature of 70° C. for 4 hours to obtain a heterofunctional ligand ZnCl(COO-PEG5-CH3). (Yield: 29%)
ZnCl(COO-PEG5-CH3) heterofunctional ligand synthesized in Synthesis Example 1 was added to 34 wt % of InP/ZnSeS nanoparticle solution (in cyclohexyl acetate) at 10 wt %, 20 wt %, or 30 wt % based on the nanoparticle, and heated at a temperature of 70° C. for 1 hour to perform a ligand exchange reaction. The reaction mixture was purified using hexane and powdered to prepare the quantum dot of Example 1.
A nanoparticle solution that had not been subjected to the ligand exchange reaction, was prepared as a quantum dot of Comparative Example 1.
Quantum dots of Comparative Examples 2 to 4 were prepared in substantially the same manner as in Example 1, except that the ligands listed in Table 1 were used instead of the heterofunctional ligands.
The luminescence efficiency (%) of each of the quantum dots of Example 1 and Comparative Examples 1 to 4, and dispersibility thereof in 1,6-hexanediol diacrylate (HDDA) were evaluated. Results are shown in Table 1.
Luminescence efficiency was measured using Otsuka Electronics' QE-2100 equipment by applying blue light in a wavelength of 450 nm and measuring the number of photons emitted compared to the number of photons absorbed. Dispersibility with respect to HDDA was evaluated by dissolving QD at 30 wt % and visually evaluating the degree of turbidity. Depending on the degree of dispersion, the evaluation results were marked as follows: if no dispersion occurs, “X,” if partially dispersed, “A,” and if completely dispersed, “O”.
With reference to Table 1 above, it was found that the quantum dot according to Example 1 was excellent in both luminescence efficiency and dispersibility. In particular, compared to Comparative Example 1, which was a crude quantum dot that did not undergo a ligand exchange reaction, the luminescence efficiency was not decreased significantly, indicating that almost no surface defects were created by the ligand exchange reaction, which was used to obtain dispersibility.
Quantum dots of Example 2 and Comparative Examples 5 to 8 were prepared in substantially the same manner as Example 1, except that CIGS/ZnS nanoparticle solution was used instead of InP/ZnSeS.
A CIGS/ZnS nanoparticle solution that had not been subjected to a ligand exchange reaction, was prepared using the quantum dot of Comparative Example 5.
Quantum dots of Comparative Examples 6 to 8 were prepared in substantially the same manner as Example 2, except that the ligands listed in Table 2 were used instead of the heterofunctional ligands.
For each of the quantum dots of Example 2 and Comparative Examples 5 to 8, the luminescence efficiency (%) and dispersibility in 1,6-hexanediol diacrylate (HDDA) were evaluated in the same manner as in Evaluation Example 1. Results thereof are shown in Table 2.
Referring to Table 2, it was found that the quantum dot according to Example 2 was excellent in both luminescence efficiency and dispersibility. In particular, the increase in the luminescence efficiency of Example 2 compared to Comparative Example 5, which relates to a crude quantum dot which had not been subjected to the ligand exchange reaction, shows that: almost no surface defects were created by the ligand exchange reaction, which is used to obtain dispersibility; and aggregation of CIGS quantum dots due to small size was prevented by ligand exchange reaction and thus, chemical stability and photoluminescence properties were increased.
Quantum dots of Example 3 and Comparative Examples 9 and 10 were prepared in substantially the same manner as Example 2, except that the ligands listed in Table 3 were used instead of the heterofunctional ligands.
For each of the quantum dots of Examples 2 and 3 and Comparative Examples 9 and 10, the luminescence efficiency (%) and dispersibility in 1,6-hexanediol diacrylate (HDDA) were evaluated in the same manner as in Evaluation Example 1. Results thereof are shown in Table 3.
With reference to Table 3, it was found that the quantum dot according to Example 3 was excellent in both luminescence efficiency and dispersibility. In particular, in the case of Comparative Examples 9 and 10, it was found that despite the use of heterofunctional ligands, the dispersibility was poor due to the inclusion of a hydrophilic group having less than 11 carbon atoms.
Quantum dots according to an embodiment may have excellent chemical stability and photoluminescence properties due to the decrease in surface defects due to substitution of ligands. In the case of such quantum dots, aggregation between nanoparticles may be prevented and thus, dispersibility in hydrophilic solvents may be excellent. Accordingly, the quantum dots may be suitable for application to ink compositions.
Accordingly, by using such quantum dots and/or methods of preparing the quantum dots, high-quality electronic devices may be provided.
The above description is an example of technical features of the disclosure, and those skilled in the art to which the disclosure pertains will be able to make various modifications and variations. Therefore, the embodiments of the disclosure described above may be implemented separately or in combination with each other.
Therefore, the embodiments disclosed in the disclosure are not intended to limit the technical spirit of the disclosure, but to describe the technical spirit of the disclosure, and the scope of the technical spirit of the disclosure is not limited by these embodiments. The protection scope of the disclosure should be interpreted by the following claims, and it should be interpreted that all technical spirits within the equivalent scope are included in the scope of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2023-0155714 | Nov 2023 | KR | national |
